It is known to provide a valve train or valve actuator assembly for an engine such as an internal combustion engine of a vehicle such as a motor vehicle. Typically, the valve train includes one or more valves, a cam shaft having one or more cams, and a tappet contacting each cam and valve. Typically, engine valve operation is accomplished via the engine-driven camshaft. However, this type of valve actuation introduces constraints on valve operation that preclude optimal valve opening and closing schedules, compromising engine performance, fuel economy, and emissions.
It is also known to provide a camless valve train for an internal combustion engine. An example of such a camless valve train is disclosed in the prior art. For example, a camless intake/exhaust valve for an internal combustion engine is controlled by a solenoid actuated fluid control valve. The control valve has a pair of solenoids that move a spool. The solenoids are digitally latched by short digital pulses provided by a microcontroller.
One class of these camless valve trains uses hydraulic fluid power to control engine valve operation. Precise engine valve positioning and seating control requires high pressure flow control. However, acceptable system performance has been achieved only with a powerful actuator driving a spool valve or an expensive two-stage servo valve.
As a result, it is desirable to provide a valve actuator assembly for an engine that achieves acceptable performance using a valve and actuator of more modest performance capability. It is also desirable to provide a valve actuator assembly for an engine that reduces cost and power consumption. It is further desirable to provide a valve actuator assembly that provides feedback to operate a valve for flow control. Therefore, there is a need in the art to provide an electrohydraulic valve actuator assembly for an engine that meets these desires.